As Mr. Erdogdu and his colleagues have found, there is little romance in the physical act of plodding for so long in heat that has often approached 100 degrees. But for some, the march has huge metaphorical meaning, prompting comparisons with the Salt March, the walk Mohandas K. Gandhi took to the Indian coast in 1930 to protest British colonial rule, which thousands of others joined.
Turkey’s marchers, led by the C.H.P.’s mild-mannered leader, Kemal Kilicdaroglu, are demonstrating against a more Turkish form of injustice. After a failed military coup last summer, President Recep Tayyip Erdogan’s government declared a state of emergency to allow the authorities to quickly round up people accused of plotting the coup. But the state of emergency has since been expanded to stifle most forms of legitimate opposition, in what Mr. Kilicdaroglu described in a roadside interview as “a civilian coup.”
And it is this crackdown that Mr. Kilicdaroglu and his fellow marchers are protesting: the arrest of 50,000 people — including, by several counts, more than 170 journalists and over a dozen lawmakers — and the dismissal or suspension of more than 140,000 Turkish workers, including several thousand academics as well as tens of thousands of teachers, prosecutors and civil servants who were believed to be critical of Turkey’s authoritarian, religiously conservative government.
As the first act of mass defiance against this purge, the march is currently “the biggest event in Turkish political life,” said one marcher, Sukru Kucuksahin. Once a prominent Turkish journalist, Mr. Kucuksahin has been jobless since being fired from a leading newspaper for writing columns critical of the government.
“The leader of the opposition,” Mr. Kucuksahin added with a hint of amazement, as if he could not quite believe what he was saying, “is marching from Ankara to Istanbul.”
The march is all the more surprising because Mr. Kilicdaroglu had previously been wary of unconventional forms of political opposition. Some have even argued that Mr. Erdogan’s continued electoral success is in part the result of Mr. Kilicdaroglu’s lack of dynamism and creativity.
But unusual times call for unusual measures. A recent referendum measure that gave Mr. Erdogan sweeping new powers highlighted the futility of following the conventional tactics of opposition. The vote was marred by voting irregularities, and the campaign that preceded it was not contested on a level playing field. Mr. Erdogan has also ruled by decree since the failed coup, undermining the role of Parliament and Mr. Kilicdaroglu’s role within it.
“With the current changes it is impossible for the opposition to talk in Parliament,” Mr. Kilicdaroglu said during a roadside interview. “The opposition has to look for other places to do its work, and in this case, it’s the march.”
As the C.H.P. is often criticized for failing to connect with citizens, the march is also an attempt to reach out beyond its traditional secularist base and build a broader coalition against Mr. Erdogan.
The route takes marchers through Turkey’s conservative heartlands that, as one C.H.P. official, Yurter Ozcan, said, “I would never in million years have even thought I’d drive through.”
As they walk, the marchers have eschewed all party branding in an effort to attract citizens of all political stripes. The real test of this approach will come toward the end of this week, when the marchers hope that tens of thousands of people will join them for the final stretch.
For the moment, the tactic seems to have had promising results. One of Mr. Erdogan’s former deputy prime ministers, Abdullatif Sener, joined the marchers for a day last week. A prominent right-wing nationalist leader, Meral Aksener, has voiced her support, as has the country’s main pro-Kurdish party. And while a majority of the marchers appear to hail from the C.H.P.’s base, they also include a number of conservative Turks.
On a recent sweltering day, the man puffing along at the front of the march was Prof. Cihangir Islam, a veteran of two Islamist parties and the former husband of Turkey’s first veiled lawmaker. Mr. Islam was purged from his university position this year after he signed a letter condemning a military campaign in several Kurdish cities.
“I had no connection with the C.H.P. before,” said Mr. Islam as he explained the varied backgrounds of the marchers. “You can observe many different kinds of social classes.”
Reaction from local residents, who voted heavily for Mr. Erdogan’s party — the Justice and Development Party, or A.K.P. — in the most recent elections, was more mixed. Well-wishers regularly flashed victory signs from their cars or stood on their balconies to applaud. One man, a nut farmer who said he usually voted for a rival opposition party, even bought lunch for several C.H.P. lawmakers.
But others also lined the route to hurl abuse at Mr. Kilicdaroglu and his supporters, who politely responded to the provocations with a round of applause. In a sign of disrespect, someone left a truckload of manure outside the site where the marchers pitched camp, and a bullet was left in the road.
Many flashed a four-fingered salute, known as the Rabia sign, that has become a symbol of support for Mr. Erdogan. Every few minutes cars would screech past — horns blaring — with a hand extending from the sunroof or window, flashing the Rabia sign.
For many residents here, Mr. Erdogan has enshrined the freedom that they care most about: the freedom to worship and express one’s faith in public. They also appreciate the improvements his party has made to Turkey’s infrastructure, health care system and social services, said one disapproving bystander, Ergun Keles, 22, a textile worker.
“They say ‘justice,’” Mr. Keles said as he waited for a bus that had been delayed by the marchers. “But I’ve been waiting half an hour in the sun. Is that justice?”
In another nearby town, Ahmet Buyukkara, a 27-year-old waiter, dismissed the march as so much posturing. “We call Kilicdaroglu the fake Gandhi,” he said. “The Chinese-made Gandhi.”
Part of this animosity has been stoked by Mr. Erdogan’s party. His allies have implied that the march put Mr. Kilicdaroglu and his colleagues in an alliance with terrorists and the plotters of last summer’s coup. Mr. Erdogan has even hinted that Mr. Kilicdaroglu may be arrested because of his role in the march.
But for now the state is allowing the march to proceed, and even granted it the protection of a group of police officers and members of the military police. As much as Mr. Erdogan would wince at the sight of thousands of antigovernment protesters marching into Istanbul, some analysts contend that he may feel he has more to lose by rounding them up and making a hero out of Mr. Kilicdaroglu.
Even some A.K.P. supporters “recognize that Kilicdaroglu has the right to march,” said Howard Eissenstat, a Turkey expert at St. Lawrence University and a nonresident senior fellow at the Project on Middle East Democracy, a think tank.
“A showdown in which that’s prevented really plays badly for a lot of Erdogan supporters, who believe in Erdogan and believe in the A.K.P. mission but expect it to be democratic,” Mr. Eissenstat added.
Mr. Kilicdaroglu is not taking anything for granted. He said he was ready to be arrested.
“If we have to pay a price,” he said as he prepared for the final stretch of the day’s marching, “we will pay for it.”